@ho_kuku
A simply apt update && apt full-upgrade should do.
The image comes with linux-image-arm64-odroid-n2 installed from Meverics APT repo that contains kernel and firmware for Odroids. Since this is a meta package that depends on the actual current kernel package (currently linux-image-4.9.185+), apt upgrade will not upgrade it, but full-upgrade is required to allow changing the dependency.